1. Field of the Invention
The present invention relates in general to pneumatic conveying systems. In particular, the present invention relates to an improved system for pneumatically conveying abrasive particulate material.
2. Description of the Related Art
The conveying and metering of particulate materials have typically been effected by one of two methods.
The first method employs a rotary air lock. The rotary air lock consists of a sectioned valve member having a plurality of radially extending plates. The valve member is located inside a cylindrical housing for rotation about a horizontal axis, such that the radially extending blades rotate like the spokes of a wheel within the housing. Material is delivered to an intake port of the housing and falls into a section of the valve member between two adjacent plates.
As the valve member rotates within the housing, each section between adjacent plates is sealed against the housing wall. This sealing minimizes the pressure drop across the air lock. As the valve member continues to rotate, each successive section between adjacent plates comes into registration with an exhaust port. The material held between the adjacent plates thus falls out of the exhaust port and onto further conveying means, such as an airstream or a belt conveyor.
The second typical method employs a pressure pot. The pressure pot consists of a chamber having an intake valve and a discharge valve. The discharge valve is first closed while the intake valve is opened. Material to be conveyed is fed from a material hopper into the chamber via the intake valve. The intake valve is then closed and the discharge valve opened. The material within the chamber thus exits the chamber through the discharge valve and falls into further conveying means, such as an airstream or a belt conveyor.
Due to the number of moving parts associated with each of these methods, they are highly unsatisfactory when the conveyed material is abrasive. While it is possible to fabricate the equipment from abrasion resistant material, this often makes the cost of the equipment economically unfeasible.